1. Field of the Invention
The present invention relates to a vehicle peripheral visual confirmation apparatus for acquiring a video image of the periphery of a vehicle and then displaying the image on a displaying member in a compartment, as well as its relevant technique.
2. Description of the Related Art
In the field of vehicles, for example, in order that drivers may easily check areas serving as dead angles in the vehicle periphery, vehicle peripheral visual confirmation apparatuses are used in which the periphery of a vehicle is image-acquired with a camera installed in the rear, the front, a side, or the like of the vehicle so that the image is displayed on a display unit such as a liquid crystal panel installed in the compartment.
Requirements placed on these vehicle peripheral visual confirmation apparatuses include, for example, the following two points.
(1) Pedestrians, obstacles, and the like in the periphery of the vehicle can be checked through a video image of a camera.
(2) At the time of moving backward, the sense of distance to obstacles such as another vehicle and a wall can be obtained with precision on the order of 10 cm or the like.
Among these, point (1) is achieved using the source video image of an ordinary camera. FIG. 5 shows an example of a source video image of the rearward of a vehicle acquired by a camera attached at the rear of the vehicle. In this source video image, the installed position of the camera 1 is fixed at height H from the ground surface as shown in FIG. 6 so that the source video image within the field of view 3 of the camera 1 is acquired as viewed aslant downward from a viewpoint.
At that time, in the source video image of FIG. 5 viewed aslant downward from a viewpoint, the installed position of the camera 1 generally differs from a person's visual confirmation height. This and other reasons do not necessarily permit easy confirmation of the distance between a perimeter obstacle and the vehicle, regardless of the above-mentioned requirement (2).
Thus, in order that the sense of distance to obstacles such as another vehicle and a wall should be obtained with precision on the order of 10 cm or the like as required in (2), a technique of viewpoint conversion such as the application of geometrical correction on the image has been used so that the source video image viewed aslant downward from a viewpoint is converted, for example, into a video image of plane view coordinates as shown in FIG. 7 so that the sense of distance would be confirmed easily.